Add lsp config for dotnet.

Author: jmoseley

.github/lsp.json

@@ -0,0 +1,12 @@
+{
+  "lspServers": {
+    "csharp": {
+      "command": "dotnet",
+      "args": ["tool", "run", "csharp-ls", "--solution", "GitHub.Copilot.SDK.sln"],
+      "fileExtensions": {
+        ".cs": "csharp"
+      },
+      "projectRootFiles": ["GitHub.Copilot.SDK.sln"]
+    }
+  }
+}

dotnet/dotnet-tools.json

@@ -0,0 +1,13 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "csharp-ls": {
+      "version": "0.21.0",
+      "commands": [
+        "csharp-ls"
+      ],
+      "rollForward": false
+    }
+  }
+}